a(n) = (n+1)^2*(n+2)*(5*n^2 + 15*n + 12)/24.

Terms

a(0) =1a(1) =16a(2) =93a(3) =340a(4) =950a(5) =2226a(6) =4606a(7) =8688a(8) =15255a(9) =25300a(10) =40051a(11) =60996a(12) =89908a(13) =128870a(14) =180300a(15) =246976a(16) =332061a(17) =439128a(18) =572185a(19) =735700a(20) =934626a(21) =1174426a(22) =1461098a(23) =1801200a(24) =2201875a(25) =2670876a(26) =3216591a(27) =3848068a(28) =4575040a(29) =5407950